(Bloomberg) - The average price for regular gasoline at U.S. pumps rose 4.74 cents in the past two weeks to $3.5572 a gallon, the highest since Sept. 20, according to Lundberg Survey Inc. The survey covers the period ended March 21 and is based on information obtained at about 2,500 filling stations by the Camarillo, Calif.-based company. The average is 15.02 cents below a year ago.

“It’s been six weeks of rising prices at the pump but this is a pace that has greatly slowed,” said Trilby Lundberg, president, Lundberg Survey. Consumers are paying more even as oil and gasoline futures have fallen because the price for ethanol, the government-mandated fuel additive, has risen, Lundberg continued. “Higher ethanol prices adds about a nickel at the pump.”

Ethanol prices have jumped 24 percent this month as winter weather and a shortage of rail cars slowed the movement of the biofuel from plants in the Midwest to fuel terminals, particularly in Chicago and the Northeast.

Highest Price

The highest price for gasoline in the lower 48 U.S. states among the markets surveyed was in Los Angeles, at $4.003 a gallon, Lundberg said. The lowest price was in Billings, Mont., where customers paid an average $3.18 a gallon. Regular gasoline averaged $3.73 a gallon on Long Island, N.Y.

Gasoline futures on the New York Mercantile Exchange fell 6.59 cents, or 2.2 percent, to $2.9079 a gallon in the two weeks ended March 21.

Inventories of motor fuel across the U.S. fell 1.47 million barrels in the week ended March 14, to 222.3 million, the Energy Information Administration reported March 19. Stockpiles have fallen four straight weeks, decreasing 11.1 million barrels.

Crude inventories climbed by 5.85 million barrels to 375.9 million last week. West Texas Intermediate crude fell $3.12, or 2.5 percent, to $99.46 a barrel on the Nymex in the two weeks to March 21.